1. Field of the Invention
The present invention relates to a corona generator used to purify automotive exhaust gases by corona discharge and for other purposes and, more particularly, to a bridged stream corona generator which can stably generate and maintain bridged stream corona discharge over an extended period of time.
2. Prior Art
One of techniques heretofore used to this end is disclosed in Japanese Patent Kokai Publication No. 57 (1982)-20510. According to the disclosure, this prior art comprises a corrugated dust collector in a cylindrical form and a desired number of discharge lines laid across a hollow portion of the dust collector. With a high voltage applied on the discharge lines, fine particles such as tar particles and graphite in exhaust gas are removed. More specifically, fine particles floating in exhaust gas are attracted and deposited on the inner wall of the cylindrical dust collector by the action of an intensive electrostatic field for their removal.
With such a prior art as mentioned above, however, it is likely that the discharge lines may be torn down, when spark discharge occurs between the dust collector and the discharge lines.
Another disadvantage is that it is still less than satisfactory in the force with which harmful gases in exhaust fumes such as NO.sub.x and CO.sub.x are attracted and deposited.
Recently, it has been proposed to make use of corona discharge as effective means for generating discharge to activate such harmful gases for their dissociation and elimination. With general corona discharge, however, it is impossible to obtain any desired force with which dust, etc. contained in exhaust gas can be attracted or dissociated.
In order to put to practical use the technique for dissociating and eliminating harmful gases by said corona discharge, on the other hand, it is required to generate specific coronas, i.e., bridged stream coronas and provide an increased generation of the bridged stream coronas.
In order to generate the bridged stream coronas stably over an extended period of time, it is then required to eliminate the influence of, for instance, the deposition of carbonized particles, etc. upon generating the bridged stream coronas.